1. Field of the Invention
The present invention relates to an improvement of a rotation angle detector comprising: a magnet attached to a rotating shaft, and magnetized in a certain direction orthogonal to an axis of the rotating shaft; and a non-rotary magneto-electric transducer placed so as to be opposed to an end surface of the magnet, and configured to detect a rotation angle of the rotating shaft in cooperation with the magnet through magneto-electric transduction.
2. Description of the Related Art
Such a rotation angle detector is already known, as disclosed in, for example, Japanese Patent Application Laid-open No. 2009-19926.
As shown in FIG. 3, in a solid cylindrical magnet 010 of such a conventional rotation angle detector, an end surface 010a facing magneto-electric transducers 015 is formed as a flat surface orthogonal to an axis Y of a rotating shaft 2. In a magnetic field M which the end surface 010a of the magnet 010 of this kind faces, the curvature of an arc-shaped magnetic flux f becomes smaller as the magnetic flux f gets farther from the end surface 010a of the magnet 010. For this reason, if the magneto-electric transducers 015 are placed sufficiently closer to the end surface 010a of the magnet 010 in order to make the rotation angle detector compact in size, even the slightest variation in a positional relationship between the magnet 010 and the magneto-electric transducers 015 due to a factor such as a change in ambient temperature or a lapse of time changes magnetism sensed by the magneto-electric transducers 015, and accordingly influences accuracy at which the rotation angle is detected. With this taken into consideration, a conventional practice adopted to stabilize the accuracy with which the rotation angle is detected is to place magnetism sensing centers C02 of the respective magneto-electric transducers 015 in a location which is relatively away from the end surface 010a of the magnet 010, and where the curvature of the arc-shaped magnetic flux f is relatively small. In this case, however, it is difficult to make the rotation angle detector compact in size.